The present invention relates to twine wrapping mechanisms for applying wraps of twine to large cylindrical bales and more particularly relates to reversible drive mechanisms for oscillating one or two twine dispensing arms back and forth between transversely spaced locations adjacent the bale forming chamber resulting in a twine end dangling from the arm or arms being fed into the bale chamber between the rotating bale and belts or rolls causing such rotation whereby a length of twine is pulled through the twine arm or arms from a supply roll or rolls.
It is known to incorporate structure in a reversible twine arm drive mechanism that results in the twine arm dwelling while the drive input continues with overlapping wraps of twine thereby being applied to a preselected circumferential zone of a bale so that the twine is securely captured on the bale. For example, U.S. Pat. No. 4,457,226 issued July 3, 1984 discloses a reversible drive incorporating a drive gear coupled to an extensible and retractable hydraulic actuator and a driven gear fixed to one end of a twine dispensing arm and meshed with the drive gear whereby extension and retraction of the actuator causes the twine dispensing arm to swing back and forth between first and second locations adjacent opposite ends of the bale-forming chamber. The gears are provided with toothless sections which come into register with each other as the arm arrives at its second location and the actuator approaches the end of its extension stroke thereby causing the arm to dwell at its second location resulting in overlapping wraps of twine being applied to the bale adjacent an end thereof. The driven gear carries an arm engageable with a spring-loaded rod which acts to ensure reengagement of the toothed portions of the gears for operation during the retraction stroke of the actuator. While this patented arrangement is effective to cause a single twine arm to dwell at one of its end locations, the specially made and arranged gears bring added cost to the manufacture and assembly of the twine dispensing arm drive.